Proteins that function in association with DNA recognize and possess an affinity for purified DNA. Affinity chromatography on DNA columns which utilizes this property of recognition will be used to characterize and selectively purify viral proteins involved in DNA replication and transcriptional controls from FV 3-infected cells. The DNA-binding proteins will be further purified by ion exchange and sephadex gel chromatography and characterized by gel electrophoresis. Two approaches will be used to determine the functions of these proteins: (1) Purified or partially purified DNA-binding proteins will be tested for enzymatic activities, e.g., DNA polymerase, transcriptase, nucleases, ligases, etc. (2) Several temperature-sensitive mutants defective in DNA replication or transcriptional controls will be screened for defective DNA-binding proteins. Presence of a defective DNA-binding protein can then be correlated to a specific defect in viral DNA replication or transcriptional control. Further experiments are planned to analyze the functions of DNA-binding proteins in greater detail.